JP2849870B2 - Method of forming bump on electronic component mounting substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention forms bumps for mounting electronic components or connecting to other substrates or the like on leads constituting an electronic component mounting substrate. How to do it.

(Prior Art) An electronic component mounting board for mounting an electronic component is formed by forming a conductor circuit for electrically connecting an electronic component or the like to an insulating base material. Various types have been proposed according to the form. Above all, various electronic component mounting substrates having a large number of leads as shown in FIG. 3 have been proposed in order to mount highly dense electronic components.

The electronic component mounting board shown in FIG. 3 is proposed in, for example, Japanese Patent Application Laid-Open No. 60-128627, but externally connecting the electronic component to leads protruding from an insulating base material. The electronic component is housed in an opening such as a device hole in which each lead is projected while connecting the terminals, thereby reducing the overall thickness. In order to adopt such a configuration, bumps must be formed on each lead side or electronic component side to electrically connect them.
Bumps are used to make electrical connections by melting them.However, when the line width between leads becomes narrower as electronic components become denser, such bumps must be formed accurately. Is the most important condition.

The bump may be formed on the external connection terminal side of the electronic component or may be formed on the lead side of the electronic component mounting board. If is incorrect,
Since such expensive electronic components cannot be used, forming a bump on the relatively inexpensive electronic component mounting substrate side has become a recent trend. That is, it is becoming mainstream that the bumps are formed on the lead side of the electronic component mounting substrate.

Therefore, the present inventors have conducted various studies on how to form a homogenized bump even if the gap and width between the leads are reduced, and as a result, completed the present invention. It is.

(Problems to be Solved by the Invention) The present invention has been made on the basis of the above circumstances, and the problem to be solved is how to form a fine but homogenized bump. Is.

It is an object of the present invention to provide a fine and uniform electronic component mounting board in which the gaps and widths between leads are becoming narrower. It is an object of the present invention to provide a method capable of forming a simplified bump very easily and surely.

(Means for Solving the Problems) In order to solve the above problems, first, means according to the first aspect of the invention will be described with reference numerals used in the embodiments. ), And has a lead (11) projecting outward or into the device hole (13a).
In (0), the electronic component (20) is attached to each lead (11).
Or a method of forming a bump (14) for mounting or electrically connecting to another substrate through the following steps.

(1) a step of previously forming each bump (14) at a predetermined position on the metal foil (11a) by means such as plating; (2) a metal foil (11a) having these bumps (14)
With respect to the substrate (12) on which an opening (13) serving as a device hole (13a) or the like is formed or an opening portion is formed.
A step of integrating the bumps (14) such that the bumps (14) are located in the openings (13) or the planned openings; (3) filling the openings (13) with a back coat material (15) made of resin or the like; Or a step of covering the whole of each bump (14) by using a base material in the opening to be opened; (4) performing predetermined etching on the metal foil (11a) to electrically separate the leads (11) from each other; (5) forming each lead (1) by removing the back coat material (15) in the opening (13) or the base material in the portion to be opened;
Step 1) of exposing each bump (14) formed in advance on the portion to be the tip. "

Also, the means adopted by the invention according to the second claim is a method similar to the method described in the first claim, which includes the following steps.

(1) Etching the metal foil (11a) and each lead (11)
Forming a solder plating (16) to be an etching resist on the surface of the metal foil (11a) so as to cover the entire bump (14); (2) forming the solder plating (16). ) Is used as an etching resist to etch the metal foil (11a) to form each lead (11); (3) Solder each bump (14) and lead (11) by reflowing the solder plating (16). And making the leads (11) electrically independent. "

(Operation and Embodiment of the Invention) The operation of each invention configured as described above will be described together with the embodiment. First, in the method according to the first claim, as shown in FIG. (1) At a predetermined position on the metal foil (11a),
It is necessary to form each bump (14) in advance by plating or the like, and such a process itself is possible in relation to the subsequent steps.
The formation of each bump (14) on the metal foil (11a)
Since the metal foil (11a) is a material constituting one plane and is made of the same kind of metal on the plane, power supply such as forming each bump (14) by electroplating is performed. It can be extremely stabilized, so that each bump (14) formed can be homogeneous. In addition, it is possible to stably form each bump (14) on a planar metal foil (11a) composed of only the same metal on a plane by chemical plating or conversely by etching. Each bump (1
4) can be formed stably.

Next, the metal foil (11a) on which the bumps (14) are formed
As shown in FIG. 1 (b), (2) a metal foil (11a) having these bumps (14) is inserted into a device hole (13).
a) The bumps (14) are integrated with the base material (12) on which the openings (13) serving as etc. are formed or formed so as to be located in the openings (13). At this time, if each bump (14) is formed on the outer lead portion of the lead (11), the opening (13) is a portion that forms the outer shape of one electronic component mounting board (10). If each bump (14) is formed in the inner lead portion of the lead (11) (the portion to which the external connection terminal of the electronic component (20) is connected), the opening (13) is formed as shown in FIG. It becomes a device hole (13a) as shown in (e) of FIG. In the examples described later, a so-called film-shaped substrate is used as the substrate (12). However, a so-called rigid substrate may be used, or a substrate made of a photosensitive liquid polyimide resin may be used. There may be. When the substrate (12) is formed of the photosensitive liquid polyimide resin, the opening (13) for projecting each lead (11) is formed after being integrated with the metal foil (11a). May be implemented.

Then, as shown in FIG. 1C, in the base material (12) in which the opening (13) to become the device hole (13a) is formed, (3) the resin is placed in the opening (13). The back coat material (15) consisting of the bumps (14)
It covers the whole. This is because in the next step (4), the metal foil (11a) is subjected to a predetermined etching while utilizing the back coat material (15) and the base material (12) to electrically separate the leads (11) from each other. ) Must be formed, but it is necessary to use the back coat material (15) as an etching resist for this etching. Therefore, the material of the back coat material (15) acts as an etching resist for the metal foil (11a), and the back coat material (15) needs to be removed in (5) later. It is necessary to use a material that is soluble in a solvent that does not dissolve the base material (12). Therefore, in the examples described later, when a copper metal foil (11a) and a polyimide base material (12) are employed, a photosensitive acrylic resin is used as a material of the back coat material (15). -ing

After that, as shown in FIG.
(4) Using the back coat material (15) and the base material (12), the metal foil (11a) is subjected to predetermined etching to form the electrically independent leads (11). In this case, a mask for forming the conductive circuit and each lead (11) must be arranged on the metal foil (11a), and the mask must be positioned with respect to each bump (14). In the embodiment, this positioning is performed as follows. That is, paying attention to the fact that the metal where the bumps (14) are formed is thicker, the position of each bump (14) is determined using a thick film meter using X-rays, Based on this position, a mask for etching the metal foil (11a) is formed. As a result, as shown in FIG. 1 (d) or (e), the bumps (14) are securely located at the tips of the leads (11).

Finally, as shown in FIG. 1 (e), (5) by removing the unnecessary back coat material (15) in the opening (13), it becomes the tip of each lead (11). By exposing each of the bumps (14) formed in advance on the portion, the electronic component mounting substrate (10) having the necessary bumps (14) is completed. This back coat material (1
The removal of 5) was performed by using a release material when this was formed of a photosensitive acrylic resin.

On the other hand, in the invention according to the second claim, step (1)
And the step (2) has the same structure and operation as those according to the first claim described above, but differs from the step (3) as follows. 2A and 2B correspond to FIGS. 1A and 1B, respectively.

As shown in (c) of FIG. 2, (3) in order to form the leads (11) by etching the metal foil (11a), solder plating (1) to be an etching resist is used.
6), while covering the whole of each bump (14),
It is formed on the surface of the metal foil (11a). In other words, in the invention according to the second claim, as an etching resist for etching for forming each lead (11) from the metal foil (11a), a portion other than a necessary conductor circuit and a portion to become the lead (11) is used. The formed solder plating (16) is used. Then, as shown in (d) of FIG.
(4) Using the solder plating (16) as an etching resist, the metal foil (11a) is etched to form each lead (11). As a result, the upper and lower sides of the drawing are covered with the solder plating (16), and the leads (11) having the necessary bumps (14) as they are are formed.

In the state shown in FIG. 1D, particularly, the inner ends of the leads (11) are short-circuited by solder plating (16), and in some cases, solder plating is performed in the middle of each lead (11). (5) The bumps (14) and the leads (11) are covered with solder by reflowing the solder plating (16). The electronic component mounting substrate (10) as shown in FIG. 2 (e) is completed by electrically isolating the electronic components.

In the method according to the second claim, since the bumps (14) after being completed as the electronic component mounting substrate (10) can be wrapped by solder plating (16), each bump (14) is By melting, it is possible to further assure the function of making electrical connection between each lead (11) and the external connection terminal of the electronic component (20).

(Effects of the Invention) As described in detail above, in each invention, each lead (1
A necessary bump (14) is formed in advance on the metal foil (11a) for forming 1) and the conductor circuit, and each lead (14) is formed from the metal foil (11a) while protecting the bump (14). 1
Because of the formation of (1), in the electronic component mounting substrate where the gap and width between the leads are becoming narrower, it is fine but homogenous that can reliably make electrical connection to electronic components etc. Thus, it is possible to provide a method capable of forming the formed bump very easily and surely.

In particular, in the invention according to the first claim, the metal foil (11
The bumps (14) formed in a) are inserted into the openings (13) in the substrate (12).
After being protected by a back coat material (15) so as to enter the inside, each lead (11) is formed by etching the metal foil (11a), which is generally performed from the prior art. It is possible to form the leads (11) that can be made fine by providing the necessary bumps (14) while using the etching method and apparatus as they are, thereby making it possible to make the electronic component mounting substrate (10) itself fine. This can be easily achieved without increasing the cost.

According to the second aspect of the invention, the lead (11)
The solder plating (16) used as an etching resist can be used as a material for forming the bump (14).
4) can be formed easily and reliably.

[Brief description of the drawings]

1 (a) to 1 (e) are partially enlarged sectional views showing the method according to the first claim in the order of steps, and FIGS. 2 (a) to 2 (e) show the method according to the second claim. FIG. 3 is a partial cross-sectional view showing a general electronic component mounting substrate having leads for mounting electronic components, and FIG. 4 is a portion in which bumps are formed by a mesa method. It is an expanded sectional view. Explanation of reference numeral 10: electronic component mounting board, 11: lead, 11a: metal foil, 12: base material, 13: opening, 13a: device hole, 1
4 ... Bump, 15 ... Back coat material, 16 ... Solder plating, 20 ... Electronic parts.

────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yasuhiro Horiba 300 Aoyagi-cho, Ogaki-shi, Gifu IBIDEN Corporation Aoyagi Factory (56) References JP-A-3-99448 (JP, A) JP-A-61-172361 (JP, A) JP-A-56-8834 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01L 21/60 311

Claims (2)

(57) [Claims] An electronic component mounting board having leads protruding outward from a base material or into a device hole for mounting an electronic component on each of the leads or making an electrical connection to another substrate. Of forming the bumps through the following steps. (1) a step of previously forming each of the bumps at a predetermined position on the metal foil by means such as plating; (2) a metal foil having these bumps is formed or scheduled to have an opening to be the device hole or the like; A step of integrating each of the bumps with the base material on which the portions are formed such that each of the bumps is located in the opening or the opening to be opened; Or, using the base material in the scheduled opening portion,
(4) performing predetermined etching on the metal foil to form the respective leads that are electrically independent from each other; (5) back coating material in the opening or the above-described method. A step of exposing each of the bumps formed in advance on a portion to be a tip of each lead by removing the base material in the portion to be opened; 2. The method according to claim 1, further comprising the following steps. (1) forming a solder plating to be an etching resist on the surface of the metal foil so as to cover the entire bumps in order to form the leads by etching the metal foil; Forming a lead by etching the metal foil using the solder plating as an etching resist; and (3) reflowing the solder plating.
While covering each of the bumps and leads with solder,
The process of electrically isolating each lead.